The inventive concept described herein relates to semiconductor memories, and more particularly, to nonvolatile memory systems and methods of operating such systems.
A semiconductor memory device can be fabricated using semiconductors such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphide (InP), and the like. Semiconductor memory devices can be classified into volatile memory devices and nonvolatile memory devices.
A volatile memory device such as a Static RAM (Static Random Access Memory), a Dynamic RAM (DRAM), a Synchronous DRAM (SDRAM), etc. may lose stored data when power to the memory is lost. A nonvolatile memory device such as a Read Only Memory (ROM), a Programmable ROM (PROM), an Electrically Programmable ROM (EPROM), an Electrically Erasable and Programmable ROM (EEPROM), a flash memory device, a Phase-change RAM (PRAM), a Magnetic RAM (MRAM), a Resistive RAM (RERAM), a Ferroelectric RAM (FRAM), etc. may retain stored data even when power is lost.
A flash memory-based solid state drive (hereinafter, referred to as “SSD”) is used in some applications. An SSD may operate at a faster speed, lower noise and lower power than a conventional hard disk drive. An SSD may also incorporate a DRAM as a buffer memory. However, because a DRAM is a volatile memory, it may be needed to copy or flush data (e.g., mapping table, metadata, etc.) stored in the DRAM into the flash memory when a sudden power-off occurs (SPO). This operation may be referred to as an SPO backup operation, and may utilize an auxiliary power device (such as a tantalum capacitor, a super capacitor, or a battery).